1. Field of the Invention
The present invention relates to a manufacturing method and a manufacturing apparatus of a semiconductor substrate.
2. Description of the Related Art
In recent years, integrated circuits using an SOI (silicon on insulator) substrate, instead of using a bulk silicon substrate, have been developed. By utilizing characteristics of a thin single crystal silicon layer formed over an insulating layer, transistors formed in the integrated circuit can be electrically separated from each other completely. Further, each transistor can be formed as a fully-depleted transistor, and thus a semiconductor integrated circuit with high added value such as high integration, high speed driving, and low power consumption can be realized.
As a method for manufacturing an SOI substrate, a hydrogen-ion-implantation separation method in which hydrogen ion implantation and separation are combined is known. A typical process of a hydrogen-ion-implantation separation method will be described below.
First, hydrogen ions are implanted into a silicon substrate to form an ion implantation layer at a predetermined depth from the surface. Next, a silicon oxide film is formed by oxidizing another silicon substrate which serves as a base substrate. After that, the silicon substrate into which hydrogen ions are implanted is disposed in close contact with the silicon oxide film of the another silicon substrate, so that the two silicon substrates are bonded to each other. Then, by performing heat treatment, one of the silicon substrates is cleaved using the ion implantation layer as a cleavage plane.
There is a known method in which a single-crystal-silicon layer is formed over a glass substrate by using a hydrogen-ion-implantation separation method (e.g., Reference 1: Japanese Published Patent Application No. Hei 11-097379). In Reference 1, a separation plane is mechanically polished in order to remove a defect layer formed by ion implantation or a step which is several to several tens of nanometers in height in the separation plane.